Two others — Nicky Foremsky and Carolyn Badila — trailed her from the drier vantage of the stream shore.

“Oh, look, it’s a turtle head,” said Thompson-Deahl, Reston Association’s environmental resources manager, pointing up to shrubs along the shoreline.

While the novice naturalist might have expected to see a box turtle romping through the underbrush, both Foremsky and Badila knew right away that Thompson-Deahl was talking about a particular flower.

“See, when you have a healthy stream, you’ll get this. It’s a build-it-and-they-will-come kind of thing,” said Badila, co-chair of RA’s Environmental Advisory Committee, referring to the stretch of the stream that had recently been restored.

Thompson-Deahl and Foremsky, RA’s watershed manager, trekked about a half-mile section of the stream, showing Badila the results of a restored stream.

What once looked like a gully framed by two vertical shorelines getting deeper from erosion were now gentle sloping edges supporting numerous native plant species.

The turtle head, a wildflower that feeds the Baltimore checker-spot Butterfly — one of countless ecological goodies offered by Thompson-Deahl — was just one indicator of how the stream had bounced back after being restored.

A FEW YEARS AGO, Fairfax County and GKY and Associates restored about 1,000 feet of Glade Stream, starting from the headwaters near the United Christian Parish on Colts Neck Road.

But in the coming years, Reston will be the beneficiary of a major stream restoration project at no cost to members.

Wetland Studies and Solutions, a Gainesville-based environmental consulting firm, plans to reverse 40 years of severe stream degradation and erosion caused by development in Reston. About 10 miles of three principal tributaries will be repaired, including Snakeden Branch, The Glade and Colvin Run.

The company is investing $35 million to complete the project over the next 10 years. The work will be converted into restoration credits, which are accumulated in a “bank.” Then, the company can then sell credits to developers who degrade or disturb streams elsewhere in the region.

The authority to swap money for restoration credits derives from the Clean Air Act, which states that banks “will be used for compensatory mitigation for unavoidable impacts to jurisdictional waters.” In the past, wetlands have been the focus of mitigation banks. This will be one of the first stream bank projects.

For Reston, it will translate into a robust watershed. “I’m extremely excited,” Foremsky said about the project. Foremsky, who started with RA last December, will work with Wetland Studies and Solutions as the project moves forward.

Much of her time will also be spent building awareness about the project.

ENVIRONMENTALLY CONSCIOUS Restonians, like Badila, say the project is just what the doctor ordered. “It’s just a gift that dropped into our laps,” said Badila.

Thompson-Deahl agrees. She said it would have been unlikely that the Association could have made a similar investment even if it wanted to. “We don’t have that kind of money,” she said, adding that staff has had to rely on inexpensive fixes here and there as well as support from the county.

Nearly four years ago, Michael Rolband, president of Wetland Solutions and Studies, worked out a deal with Reston Association to set up the stream "bank," called the Northern Virginia Stream Restoration Bank.

Chuck Veatch, a longtime Reston resident, business owner and local photographer, is credited with bringing the two parties together.

Both Thompson-Deahl and Foremsky say that the difference to the streams once the project is done will be night and day. In addition, the restoration work will make the surrounding natural areas more attractive to wildlife, big and small.

To date, Wetland Studies and Solutions has inventoried and mapped about 20,000 trees. Restoration work is scheduled to begin early next year.

WHILE THE PROJECT will require some tree removal, both Foremsky and Thompson-Deahl say it will be supplemented with new plantings. “You can bet there will be a lot of tree replacement,” said Thompson-Deahl.

She points out that right now erosion may be the greatest threat to trees. “They are going to go anyway if you don’t do anything,” said Thompson-Deahl, as she points to a degraded bank where several trees’ root systems are exposed. “That’s just a perfect example of a degraded stream. There’s no flood plain.”

The project will also bring in additional light along some sections of the stream, said Foremsky. “Letting in the light is very important, especially for these plants along the stream,” said Foremsky.

Wetland Studies and Solutions will monitor the restored streams for 10 years after the completion of the project, ensuring the sustainability of the work.

After that, RA will help maintain the network of healthy streams. “That’s why we have watershed people on staff [now] — to do repairs that need to be done,” said Thompson-Deahl.